Method for transmitting or receiving signal using long sequence and apparatus therefor

ABSTRACT

The present document relates to a method for transmitting a signal using a long sequence in a wireless communication system. According to the method, a transmission side device transmits a signal using the long sequence comprising a combination of a plurality of sub-subsequences, wherein each of the plurality of sub-subsequences comprises a combination of a plurality of short base sequences, each having a length equal to or shorter than a predetermined length, and sequences obtained by multiplying each of the base sequences by a cover sequence.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage filing under 35 U.S.C. 371 ofInternational Application No. PCT/KR2016/011826, filed on Oct. 20, 2016,which claims the benefit of U.S. Provisional Application No. 62/244,200,filed on Oct. 21, 2015, the contents of which are all herebyincorporated by reference herein in their entirety.

TECHNICAL FIELD

The present invention relates to a method for generating a long sequencebased on a short sequence in a wireless communication system and acommunication method and apparatus using the same.

BACKGROUND ART

Recently, demand for IoT technology has increased and narrowband IoT(NB-IoT) technology has been discussed in order to support such an IoTservice. NB-IoT seeks to provide appropriate throughput betweenconnected apparatuses despite low apparatus complexity and low powerconsumption.

In 3GPP of the NB-IoT standards, NB-IoT technology capable of beingcombined with other 3GPP technologies such as GSM, WCDMA or LTE has beenstudied. To this end, a resource structure which will be used from theviewpoint of a legacy system has been discussed.

FIG. 1 is a diagram illustrating three modes which may be used inNB-IoT.

In order to satisfy the above-described demand, in NB-IoT, a channelbandwidth of 180 kHz is being considered for use both on uplink anddownlink, which corresponds to one physical resource block (PRB) in anLTE system.

As shown in FIG. 1, NB-IoT may support three modes such as standaloneoperation, guard band operation and inband operation. In particular, inthe inband mode shown in the lower side of FIG. 1, NB-IoT operation maybe performed through a specific narrowband in an LTE channel bandwidth.

In addition, in NB-IoT, using an extended DRX cycle, half-duplex FDD (HDFDD) operation and a single receive antenna in a wireless apparatussubstantially reduce power and cost.

DISCLOSURE OF THE INVENTION Technical Task

To achieve the above-described NB IoT operation, it is required totransmit NB synchronization signals. Specifically, since the NB IoToperation requires a specific narrowband as illustrated in FIG. 1, andthus, there is a need for a method for efficiently transmitting primarysynchronization signals (PSSs) and secondary synchronization signals(SSSs).

In some circumstances of the wireless communication system, either thePSS or SSS should represent the entirety of a cell identifier.Therefore, there is an increasing need for a sequence longer than thecurrently used sequence.

Moreover, when such a long sequence is generated, auto-correlation(autocorrelation) properties need to be researched to facilitatedetection of the signal.

Technical Solutions

To achieve these objects and other advantages, in an aspect of thepresent invention, provided herein is a method for transmitting anarrowband (NB) synchronization signal to at least one user equipment(UE) by an evolved node B (eNB) in a wireless communication system,including: repeating a Zadoff-Chu sequence having a predetermined lengthon a plurality of orthogonal frequency division multiplexing (OFDM)symbols in a frequency domain and transmitting the repeated Zadoff-Chusequence as an NB primary synchronization signal (NB PSS); andtransmitting an NB secondary synchronization signal (NB SSS) foridentifying an NB cell identifier. In this case, the NB PSS may betransmitted in a state in which the Zadoff-Chu sequence is multiplied ineach of the plurality of OFDM symbols by each element of a predeterminedcover sequence having a length corresponding to the number of theplurality of OFDM symbols.

In another aspect of the present invention, provided herein is a methodfor receiving a narrowband (NB) synchronization signal from an evolvednode B (eNB) by a user equipment (UE) in a wireless communicationsystem, including: receiving an NB primary synchronization signal (NBPSS) generated by repetition of a Zadoff-Chu sequence having apredetermined length on a plurality of orthogonal frequency divisionmultiplexing (OFDM) symbols in a frequency domain; and receiving an NBsecondary synchronization signal (NB SSS) for identifying an NB cellidentifier. In this case, the NB PSS may be received in a state in whichthe Zadoff-Chu sequence is multiplied in each of the plurality of OFDMsymbols by each element of a predetermined cover sequence having alength corresponding to the number of the plurality of OFDM symbols.

In a further aspect of the present invention, provided herein is anevolved node B (eNB) for transmitting a narrowband (NB) synchronizationsignal to at least one user equipment (UE) in a wireless communicationsystem, including: a processor configured to generate an NB primarysynchronization signal (NB PSS) by repeating a Zadoff-Chu sequencehaving a predetermined length on a plurality of orthogonal frequencydivision multiplexing (OFDM) symbols in a frequency domain and generatean NB secondary synchronization signal (NB SSS) for identifying an NBcell identifier; and a transceiver connected to the processor andconfigured to transmit the NB PSS and the NB SSS to the at least one UE.In this case, the processor may be configured to generate the NB PSS bymultiplying, in each of the plurality of OFDM symbols, the Zadoff-Chusequence and each element of a predetermined cover sequence having alength corresponding to the number of the plurality of OFDM symbols.

In a still further aspect of the present invention, provided herein is auser equipment (UE) for receiving a narrowband (NB) synchronizationsignal from an evolved node B (eNB) in a wireless communication system,including: a transceiver configured to receive an NB primarysynchronization signal (NB PSS) generated by repetition of a Zadoff-Chusequence having a predetermined length on a plurality of orthogonalfrequency division multiplexing (OFDM) symbols in a frequency domain andreceive an NB secondary synchronization signal (NB SSS) for identifyingan NB cell identifier; and a processor configured to process the NB PSSand the NB SSS received by the transceiver. In this case, the NB PSS maybe received in a state in which the Zadoff-Chu sequence is multiplied ineach of the plurality of OFDM symbols by each element of a predeterminedcover sequence having a length corresponding to the number of theplurality of OFDM symbols.

Advantageous Effects

According to the present invention, it is possible to efficientlytransmit synchronization signals for IoT services in the next-generationwireless communication system.

DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating three modes which may be used inNB-IoT.

FIGS. 2 and 3 are diagrams showing a method of transmittingsynchronization signals in the case of using a normal CP and an extendedCP.

FIG. 4 is a diagram showing two sequences in a logical regioninterleaved and mapped in a physical region.

FIG. 5 is a diagram showing the overall structure in whichsynchronization signals are transmitted and received in an NB LTEsystem.

FIG. 6 is a diagram illustrating the result of auto-correlation ofsequence S in Equation 3.

FIG. 7 is a diagram illustrating the result of auto-correlation ofsequence Ss in Equation 3.

FIG. 8 is a diagram illustrating a method for generating a long sequencewith good auto-correlation properties according to an embodiment of thepresent invention.

FIG. 9 is a diagram illustrating in detail a method for transmitting anNB-PSS by repetition in a plurality of OFDM symbols.

FIG. 10 is a diagram illustrating correlation properties of a pair oflength-10 complementary sequences a(n) and b(n) and various c(n)patterns.

FIG. 11 is a diagram illustrating the concept of NB-SSS transmissionaccording to an embodiment of the present invention.

FIG. 12 is a diagram illustrating a method for generating andtransmitting an NB-SSS according to an embodiment of the presentinvention.

FIG. 13 is diagram illustrating a method for selecting root indices of aZC sequence to be used for an NB-SSS according to an embodiment of thepresent invention.

FIG. 14 is a diagram illustrating cross-correlation values when aspecific Hadamard sequence is used for an NB-SSS according to anembodiment of the present invention.

FIG. 15 illustrates an exemplary downlink/uplink (DL/UL) slot structureof the wireless communication system.

FIG. 16 illustrates an exemplary DL subframe structure used in thewireless communication system.

FIG. 17 is a block diagram illustrating the components with of atransmitting device 10 and a receiving device 20 for implementing theembodiments of the present invention.

BEST MODE FOR INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. The detailed description set forth below in connection withthe appended drawings is intended as a description of exemplaryembodiments and is not intended to represent the only embodimentsthrough which the concepts explained in these embodiments can bepracticed.

The detailed description includes details for the purpose of providingan understanding of the present invention. However, it will be apparentto those skilled in the art that these teachings may be implemented andpracticed without these specific details. In some instances, well-knownstructures and devices are omitted in order to avoid obscuring theconcepts of the present invention and the important functions of thestructures and devices are shown in block diagram form.

As described above, the present invention relates to a method forgenerating a long sequence by concatenating short base sequences andefficiently transmitting a synchronization signal using the longsequence. First, synchronization signals for NB IoT operation areassumed to transmit such a long-length signal. In addition, sincesynchronization signals of the LTE system can be reused as thesynchronization signals for the NB-IoT operation, the synchronizationsignals (SSs) of the LTE system will be described in detail beforetransmission and reception of the NB synchronization signals.

FIGS. 2 and 3 are diagrams showing a method of transmittingsynchronization signals in the case of using a normal CP and an extendedCP.

The SS includes a PSS and an SSS and is used to perform cell search.FIGS. 2 and 3 show frame structures for transmission of the SSs insystems using a normal CP and an extended CP, respectively. The SS istransmitted in second slots of subframe 0 and subframe 5 inconsideration of a GSM frame length of 4.6 ms for ease of inter-RATmeasurement and a boundary of the radio frame may be detected via anSSS. The PSS is transmitted in a last OFDM symbol of the slot and theSSS is transmitted in an OFDM symbol located just ahead of the PSS. TheSS may transmit a total of 504 physical layer cell IDs via a combinationof three PSS and 168 SSSs. In addition, the SS and the PBCH aretransmitted in 6 RBs located at the center of the system bandwidth andmay be detected or decoded by the UE regardless of transmissionbandwidth.

The transmit diversity scheme of the SS uses a single antenna port andis not separately defined in the standard. That is, single antennatransmission or a transmission method (e.g., PVS, TSTD or CDD)transparent to a UE may be used.

Meanwhile, hereinafter, processes of encoding a PSS and an SSS will bedescribed.

In a PSS code, a length-63 Zadoff-Chu (ZC) sequence is defined in thefrequency domain and is used as a sequence of a PSS. The ZC sequence isdefined by Equation 1 and a sequence element n=31 corresponding to a DCsubcarrier is punctured. In Equation 1 below, Nzc=63.

$\begin{matrix}{{d_{u}(n)} = e^{{- j}\frac{\pi\;{{un}{({n + 1})}}}{N_{ZC}}}} & \lbrack {{Equation}\mspace{14mu} 1} \rbrack\end{matrix}$

The remaining 9 subcarriers of 6 RBs (=72 subcarriers) of the centerpart are always transmitted with a value of 0 and cause a filter forperforming synchronization to be easily designed. In order to define atotal of 3 PSSs, in Equation 1, values of u=25, 29 and 34 are used. Atthis time, 29 and 34 have a conjugate symmetry relation and thuscorrelations therefor may be simultaneously performed. Conjugatesymmetry means a relation of Equation 2 below. Using these properties, aone-shot correlator for u=29 and 34 may be implemented and a totalcomputational load may be reduced by about 33.3%.d _(u)(n)=(−1)^(n)(d _(N) _(ZC) _(−u)(n))*,when N _(ZC) is even number.d _(u)(n)=(d _(N) _(ZC) _(−u)(n))*,when N _(ZC) is oddnumber.  [Equation 2]

Next, encoding of the SSS will be described.

A sequence used for the SSS is configured by interleaving two length-31m-sequences and combining the two sequences, and it transmits 168 cellgroup IDs. The m-sequence used as the sequence of the SSS is robust in afrequency selective environment and a computational load may be reducedby fast m-sequence transformation using Fast Hadamard Transform. Inaddition, configuration of the SSS using two short codes is proposed inorder to reduce the computational load of the UE.

FIG. 4 is a diagram showing two sequences in a logical regioninterleaved and mapped in a physical region.

When the two m-sequences used to generate the SSS code are respectivelydefined as S1 and S2, if the SSS of subframe 0 transmits a cell group IDusing a combination of (S1, S2), the SSS of subframe 5 transmits a cellgroup ID after swapping (S1, S2) with (S2, S1), thereby identifying a10-ms frame boundary. At this time, the used SSS code uses a polynomialof x⁵+x²+1 and a total of 31 codes may be generated via differentcircular shifts.

In order to enhance reception performance, two different PSS-basedsequences may be defined and scrambled with the SSS and differentsequences are scrambled with S1 and S2. Thereafter, an S1-basedscrambling code is defined to perform scrambling with S2. At this time,the code of the SSS is swapped in units of 5 ms, but the PSS-basedscrambling code is not swapped. The PSS-based scrambling code is definedin six cyclic shift versions according to the PSS index in them-sequence generated from the polynomial of x⁵+x³+1 and the S1-basedscrambling code is defined in eight cyclic shift versions according tothe index of S1 in the m-sequence generated from the polynomial ofx⁵+x⁴+x²+x¹+1.

Cell search in NB-IoT or NB-LTE which is a model obtained by applyingNB-IoT to an LTE system is the same as the above-described LTE system. Aused sequence needs to be modified according to NB-LTE properties and,hereinafter, portions to be modified as compared to the LTE system willbe focused upon.

FIG. 5 is a diagram showing the overall structure in whichsynchronization signals are transmitted and received in an NB LTEsystem.

As shown in FIG. 5, even in the NB-LTE system, a PSS and an SSS aredivided and transmitted and are respectively referred to as NB-PSS andNB-SSS in order to be distinguished from the legacy PSS and SSS.However, a PSS and an SSS may be used if such use will not lead toconfusion.

Even in the NB-LTE system, similarly to the legacy LTE system, 504 NBcell identities through a synchronization channel need to be indicated.In the NB-LTE system according to the embodiment of the presentinvention, the NB-PSS is transmitted using one specific sequence.Therefore, the 504 NB cell identities need to be indicated using theNB-SSS only.

In a receiving device, auto-correlation is generally performed to detectthe PSS. To this end, the receiving device attempts to detect the PSSusing a sliding window method in the time domain. The method ofdetecting the PSS may increase complexity of the receiving device andthus may not be suitable for the NB-LTE system for decreasingcomplexity. Since the NB-PSS according to the present embodiment istransmitted using one specific sequence, the receiving device mayperform only operation for detecting the specific sequence, therebyreducing complexity. For example, if a Zadoff-Chu (ZC) sequence is usedfor the NB-PSS, the root index of this ZC sequence may be fixed to onepredetermined value (e.g., u=5). Since the NB-PSS is simply configured,the NB-SSS needs to be used to efficiently indicate the 504 cellidentities, which will be described below as another aspect of thepresent invention.

In one embodiment of the present invention, the NB-PSS may be repeatedlytransmitted in a plurality of OFDM symbols. Although the NB-PSS isrepeatedly transmitted in nine OFDM symbols in the example of FIG. 5,the number of OFDM symbols is not limited thereto. Since one subframeusing an extended CP may include 12 OFDM symbols and the first threeOFDM symbols of the 12 OFDM symbols may be used to transmit a PDCCH, theNB-PSS is repeatedly transmitted in the nine OFDM symbols in the exampleof FIG. 5. The above-described numerical values may be changed accordingto change in the number of OFDM symbols included in one subframe of theNB-LTE system and a maximum number of OFDM symbols required to transmitthe PDCCH. For example, if the number of OFDM symbols included in onesubframe is 14 and a maximum number of OFDM symbols used to transmit aPDCCH is 3, the number of OFDM symbols in which the NB-PSS is repeatedlytransmitted may be 11. In the present embodiment, the NB-PSS may berepeatedly transmitted in a plurality of OFDM symbols which iscontinuously arranged in the time domain.

If the NB-PSS corresponds to resource elements for transmitting a CRS inan LTE system for providing an NB-LTE service upon mapping to resourceelements in the time-frequency domain, the NB-PSS element may bepunctured to prevent collision. That is, the transmission position ofthe NB-PSS/NB-SSS may be designed to avoid collision with legacy LTEsignals such as a PDCCH, a PCFICH, a PHICH and an MBSFN.

As the NB-PSS is repeatedly transmitted in the plurality of OFDMsymbols, the receiving device may easily determine a subframe timing anda frequency offset.

Meanwhile, it is also desirable that the NB-SSS is transmitted in aplurality of OFDM symbols as shown in FIG. 5. However, since the NB-SSSshould be able to identify the entirety of a cell identifier asdescribed above, the present invention proposes a method for generatinga long sequence and transmitting the long sequence using a plurality ofOFDM symbols. Although FIG. 5 shows that the NB-SSS is transmitted insix OFDM symbols, the present invention is not limited thereto. Forexample, the NB-SSS may be transmitted in eleven OFDM symbols like theabove-described NB-PSS.

Method for Generating a Long Sequence

Hereinafter, a description will be given of a method for improvingauto-correlation performance when a long-length sequence is generated byconcatenating existing short-length base sequences. In this case, theauto-correlation properties may vary according to the arrangement orderof the short-length base sequences and how the short-length basesequences are combined with a code cover. The following embodiments aredesigned such that in the auto-correlation, the second highest peakvalue is equal to or smaller than ⅛ of the highest peak (that is, adifferent therebetween should be equal to or greater than 9 dB).

For example, by combining length-10 binary Golay sequences a(n) andb(n), it is possible to generate the following sequence S and sequenceSc, each having a total length of 80.a(n):(1,1,−1,1,−1,1,−1,−1,1,1)b(n):(1,1,−1,1,1,1,1,1,−1,−1)Sequence S:(an,an,an,an,−an,−an,−an,−an)Sequence Sc:(an,an,bn,−bn,an,−an,bn,bn)  [Equation 3]

Of course, other arbitrary sequences can be used instead of the binaryGolay sequence.

To generate the sequence S, the base sequence a(n) is repeated eighttimes. In addition, different code covers are applied to the first fourbase sequences (first four ans) and the last four base sequences (lastfour ans) of the sequence S with the total length of 80. To generate thesequence Sc, the base sequences a(n) and b(n) are repeated four times,respectively and then cover codes are applied. Hereinafter, theauto-correlation of the two sequences will be described.

FIG. 6 is a diagram illustrating the result of auto-correlation of thesequence S in Equation 3. Specifically, FIG. 6 shows theauto-correlation result of the length-80 sequence S.

Referring to FIG. 6, it can be seen that when the auto-correlation ofthe sequence S is performed, many spikes with various sizes aregenerated, and particularly, a difference between the largest spike andthe second largest spike is equal to or smaller than 3 dB. The reasonfor why the spikes are repeatedly generated is that in a specific case,the code covers applied to the sequence S create opposite phases so thatoffset synthesis is induced, but in many cases, the code covers createspikes because complementary synthesis is induced. Table 1 below showscases where spikes occur.

TABLE 1 Sequence an an an An −an −an −an −an Inner Product Result 0sample an an an An −an −an −an −an 80 (10+ 10+ 10+ 10+ 10+ 10+ 10+ 10)shifted 10 samples an an An an −an −an −an 50 (10+ 10+ 10− 10+ 10+ 10+10) shifted 20 samples an An an an −an −an 20 (10+ 10− 10− 10+ 10+ 10)shifted 30 samples An an an An −an −10(10− 10− 10− 10+ 10) shifted 40samples an an An an −40(−10 −10 −10 −10) shifted 50 samples an An an−30(−10 −10 −10) shifted 60 samples An an −20(−10 −10) shifted 70samples an −10(−10) shifted

In Table 1, an·an^(H)=10.

Meanwhile, in the case of the sequence which causes the above-describedauto-correlation results, that is, when the difference between thelargest spike and second largest spike is small or when many spikesoccur, it may not be used for signal detection in a multipathenvironment because errors occur frequently during the signal detectionTherefore, when short-length base sequences are concatenated to generatea long-length sequence, a method for guaranteeing good auto-correlationproperties needs to be devised.

FIG. 7 is a diagram illustrating the result of auto-correlation of thesequence Ss in Equation 3.

Referring to FIG. 7, it can be seen that when the auto-correlation ofthe sequence Sc is performed, a different between the largest spike andthe second largest spike is equal to or greater than 8 dB.

It is possible to configure various lengths of sequences throughcombinations of base sequences and code covers, and more particularly,the sequence may have different auto-correlation properties according tohow the base sequences and code covers are combined. Hereinafter, adescription will be given of a sequence concatenation method forallowing a long-length sequence to have good auto-correlation propertieswhen the long-length sequence is generated by concatenating short-lengthbase sequences.

FIG. 8 is a diagram illustrating a method for generating a long sequencewith good auto-correlation properties according to an embodiment of thepresent invention.

First, it is assumed in the present embodiment that M N-length basesequences (801) are combined to configure a sub-sequence (802). AlthoughFIG. 8 shows that sub-sequence A (802) includes two base sequences anand bn for convenience of description, the present invention is notlimited thereto.

Meanwhile, a new sub-sequence can be generated by applying a code coversto the base sequences (an and bn) constituting the sub-sequence (802).FIG. 8 shows that a cover sequence [−1, −1] is multiplied with [an, bn]constituting the sub-sequence A in order to generate sub-sequence −A.However, the present invention is not limited thereto, and coversequences can be applied in various ways to generate sub-sequences.

Thereafter, the final sequence can be generated by selecting andarranging L sub-sequences from the generated sub-sequence set. In thiscase, it is desirable to configure the sub-sequence combination suchthat the final sequence can satisfy the following requirements.

When the auto-correlation is calculated based on a sliding window, it isdesirable to configure a sequence queue such that the multiplicationresult of the base sequences has a different phase if the inner productis applied to some elements of the sub-sequence and the multiplicationresult of the base sequences has the same phase if the inner product isapplied to all elements.

In addition, ‘+/−1’, ‘+/−j’, etc. can be used as the cover code. Varioussequences such as complementary Golay sequence, Zadoff-Chu sequence,M-sequence, etc. can be used as the base sequence, but for convenienceof description, the following explanation will be made on the assumptionthat the complementary Golay sequence is used.

For example, a sub-sequence can be constructed using length-N basesequences an and bn. Specifically, to construct the sub-sequence, twobase sequences are concatenated and an orthogonal code cover is appliedto the concatenated two base sequences.

By doing so, sub-sequences A=[an an], B=[bn bn], C=[an bn], and D=[bnan] are constructed. If the code cover is introduced, new sub-sequencesAc=[an−an], Bc=[bn−bn], Cc=[an−bn], and Dc=[bn−an] can be generated.

To simplify calculation, the inner product of an and bn can be definedas shown in Equation 4.an·an ^(H) =bn·bn ^(H)=1an·bn ^(H) =bn·an ^(H)=0  [Equation 4]

The inner product of A=[an an], B=[bn bn], C=[an bn], and D=[bn an] canbe expressed as shown in Equation 5.A·A ^(H) =an·an ^(H) +an·an ^(H)=2B·B ^(H) =bn·bn ^(H) +bn·bn ^(H)=2C·C ^(H) =an·an ^(H) +bn·bn ^(H)=2D·D ^(H) =bn·bn ^(H) +an·an ^(H)=2  [Equation 5]

In this case, the sub-sequences Ac and Bc, the sub-sequences A and B,the sub-sequences Cc and Dc, and the sub-sequences C and D, which aregenerated by the introduction of the code cover according to thedefinition, are respectively orthogonal to each other.A·A _(c) ^(H) =an·an ^(H) −an·an ^(H)=0A·B _(c) ^(H) =an·bn ^(H) −an·bn ^(H)=0B·A _(c) ^(H) =bn·an ^(H) −bn·an ^(H)=0B·Bi _(c) i=bn·bn ^(H) −bn·bn ^(H)=0C·C _(c) ^(H) =an·an ^(H) −bn·bn ^(H)=0C·D _(c) ^(H) =an·bn ^(H) −bn·an ^(H)=0D·C _(c) ^(H) =bn·an ^(H) −an·bn ^(H)=0C·D _(c) ^(H) =bn·bn ^(H) −an·an ^(H)=0  [Equation 6]

On the contrary, the sub-sequences Ac and Bc, the sub-sequences C and D,the sub-sequences Cc and Dc, and the sub-sequences A and B are notorthogonal to each other.A·C _(c) ^(H) =an·an ^(H) −an·bn ^(H)=1A·D _(c) ^(H) =an·bn ^(H) −an·an ^(H)=−1B·C _(c) ^(H) =bn·an ^(H) −bn·bn ^(H)=−1B·D _(c) ^(H) =bn·bn ^(H) −bn·an ^(H)=1C·A _(c) ^(H) =an·an ^(H) −bn·an ^(H)=1C·B _(c) ^(H) =an·bn ^(H) −bn·bn ^(H)=−1D·A _(c) ^(H) =bn·an ^(H) −an·an ^(H)=−1D·B _(c) ^(H) =bn·bn ^(H) −an·bn ^(H)=1  [Equation 7]

According to the present embodiment, it is possible to divide thesub-sequences into sub-sequence set1 (A, B, Ac, Bc) and sub-sequenceset2 (C, D, Cc, Dc), select sub-sequences from each set, and thenproperly arrange the selected sub-sequences. By doing so, the finalsequence can be generated as described in the following embodiments.

Embodiment 1—A Case in which Set 1 is Used

(1) A Configuration Method Using Two Sub-Sequences

A random sub-sequence is selected as the first sub-sequence, and asub-sequence different from the first sub-sequence can be selected asthe second sub-sequence. The priority for selecting the secondsub-sequence from among candidates is as follows.

Priority 1. A sub-sequence having an OCC and a base sequence differentfrom those of the first sub-sequence is selected.

Priority 2. A sub-sequence having an OCC different from that of thefirst sub-sequence and the same base sequence as that of the firstsub-sequence is selected.

Priority 3. A sub-sequence with the same OCC as that of the firstsub-sequence and a base sequence different from that of the firstsub-sequence is selected.

Table 2 below shows an example of using two sub-sequences as describedabove.

TABLE 2 Sub-sequence arrangement Sequence Auto-correlation result A Bc(an an bn −bn) 0 0 0 4 A Ac (an an an −an) 1 0 1 4 A B (an an bn bn) 0 02 4

(2) A Configuration Method Using Four Sub-Sequences

It is preferable to select the third sub-sequence from among theremaining sub-sequences, which are not selected in the previous process,according to the following priority.

Priority 1. A sub-sequence having an OCC different from that of thefirst sub-sequence and the same element as that of the firstsub-sequence is selected.

Priority 2. A sub-sequence having an OCC and an element different fromthose of the first sub-sequence is selected.

Priority 3. A sub-sequence having the same OCC as that of the firstsub-sequence and an element different from that of the firstsub-sequence is selected.

Table 3 below shows an example of using three sub-sequences as describedabove.

TABLE 3 Sub-sequence arrangement Sequence Auto-correlation result A BcAc (an an bn −bn an −an) 1 0 1 0 1 6 A Bc B (an an bn −bn bn bn) 0 0 1 00 6 A Ac Bc (an an an −an bn −bn) 0 0 1 0 1 6 A Ac B (an an an −an bnbn) 0 0 1 0 2 6 A B Ac (an an bn bn an −an) 1 0 1 0 1 6 A B Bc (an an bnbn bn −bn) 0 0 1 0 2 6

In the present embodiment, the remaining sub-sequence which is notselected in the previous process can be configured as the fourthsub-sequence.

Table 4 below shows an example of using four sub-sequences as describedabove.

TABLE 4 Sub-sequence arrangement Sequence Auto-correlation result A BcAc B (an an bn −bn an −an bn bn) 0 0 0 0 0 0 0 8 A Bc B Ac (an an bn −bnbn bn an −an) 1 0 1 0 1 0 1 8 A Ac Bc B (an an an −an bn −bn bn bn) 0 00 0 0 0 0 8 A Ac B Bc (an an an −an bn bn bn −bn) 0 0 0 0 2 0 2 8 A B AcBc (an an bn bn an −an bn −bn) 0 0 2 0 2 0 0 8 A B Bc Ac (an an bn bn bn−bn an −an) 1 0 1 0 1 0 1 8

(3) A Configuration Method Using Eight Sub-Sequences

The previously selected sub-sequences can be used one more time. In thiscase, it is preferable to configure a sub-sequence queue such that thepattern made by the first four sub-sequences is not repeated.

For example, if the sub-sequence queue is (A Ac Bc B), the sub-sequencesneeds to be selected and arranged such that the pattern made by two,three, or four sub-sequences does not include (A Ac), (Ac Bc), (Bc B),(A Ac Bc), (Ac Bc B), or (A Ac Bc B).

The fifth sub-sequence is selected according to the following priority.

Priority 1. The fourth sub-sequence is selected.

-   -   This is advantageous in that even if the sub-sequence queue is        made by selecting any sub-sequences and concatenating the        selected one after the fourth sub-sequence, the sub-sequence        queue can have a pattern different from that made by the four        sub-sequences.

Priority 2. A sub-sequence with an OCC different from that of the fourthsub-sequence is selected.

Tables 5 to 7 below shows three examples of using 8 sub-sequences. InTables 5 to 7, ‘x’ indicates a sequence with poor auto-correlationproperties, and ‘o’ indicates a sequence with good auto-correlationproperties, that is, a sequence suitable for use.

TABLE 5 # of base Sub-sequence # of base Sub-sequence sequence Indexarrangement sequence Index arrangement 4 S1 A Ac 4 S1 A Ac 6 A Ac B 6 AAc Bc x 8 S11 A Ac B Bc o 8 S12 A Ac Bc B x 12 S111 A Ac B Bc A Ac x 12S121 A Ac Bc B A Ac x 16 S1111 A Ac B Bc A Ac B x 16 S1211 A Ac Bc B AAc B Bc Bc x 16 S1112 A Ac B Bc A Ac Bc x 16 S1212 A Ac Bc B A Ac Bc B Bo 12 S112 A Ac B Bc A B x 12 S122 A Ac Bc B A B x 16 S1121 A Ac B Bc A BAc x 16 S1221 A Ac Bc B A B Ac Bc Bc x 16 S1122 A Ac B Bc A B Bc x 16S1222 A Ac Bc B A B Bc Ac Ac o 12 S113 A Ac B Bc A Bc o 12 S123 A Ac BcB A Bc x 16 S1131 A Ac B Bc A Bc Ac x 16 S1231 A Ac Bc B A Bc Ac B B x16 S1132 A Ac B Bc A Bc B x 16 S1232 A Ac Bc B A Bc B Ac Ac o 12 S114 AAc B Bc Ac A o 12 S124 A Ac Bc B Ac A x 16 S1141 A Ac B Bc Ac A B x 16S1241 A Ac Bc B Ac A B Bc Bc x 16 S1142 A Ac B Bc Ac A Bc x 16 S1242 AAc Bc B Ac A Bc B B x 12 S115 A Ac B Bc Ac B o 12 S125 A Ac Bc B Ac B x16 S1151 A Ac B Bc Ac B A x 16 S1251 A Ac Bc B Ac B A Bc Bc x 16 S1152 AAc B Bc Ac B Bc o 16 S1252 A Ac Bc B Ac B Bc A A o 12 S116 A Ac B Bc AcBc x 12 S126 A Ac Bc B Ac Bc x 16 S1161 A Ac B Bc Ac Bc A x 16 S1261 AAc Bc B Ac Bc A B B o 16 S1162 A Ac B Bc Ac Bc B x 16 S1262 A Ac Bc B AcBc B A A o 12 S117 A Ac B Bc B A o 12 S127 A Ac Bc B B A x 16 S1171 A AcB Bc B A Ac x 16 S1271 A Ac Bc B B A Ac Bc Bc o 16 S1172 A Ac B Bc B ABc o 16 S1272 A Ac Bc B B A Bc Ac Ac o 12 S118 A Ac B Bc B Ac o 12 S128A Ac Bc B B Ac x 16 S1181 A Ac B Bc B Ac A o 16 S1281 A Ac Bc B B Ac ABc Bc o 16 S1182 A Ac B Bc B Ac Bc x 16 S1282 A Ac Bc B B Ac Bc A A x 12S119 A Ac B Bc B Bc o 12 S129 A Ac Bc B B Bc x 16 S1191 A Ac B Bc B Bc Ax 16 S1291 A Ac Bc B B Bc A Ac Ac x 16 S1192 A Ac B Bc B Bc Ac o 16S1292 A Ac Bc B B Bc Ac A A o 12 S11a A Ac B Bc Bc A o 12 S12a A Ac Bc BBc A x 16 S11a1 A Ac B Bc Bc A Ac x 16 S12a1 A Ac Bc B Bc A Ac B B o 16S11a2 A Ac B Bc Bc A B o 16 S12a2 A Ac Bc B Bc A B Ac Ac o 12 S11b A AcB Bc Bc Ac o 12 S12b A Ac Bc B Bc Ac o 16 S11b1 A Ac B Bc Bc Ac A x 16S12b1 A Ac Bc B Bc Ac A B B x 16 S11b2 A Ac B Bc Bc Ac B x 16 S12b2 A AcBc B Bc Ac B A A o 12 S11c A Ac B Bc Bc B x 12 S12c A Ac Bc B Bc B x 16S11c1 A Ac B Bc Bc B A x 16 S12c1 A Ac Bc B Bc B A Ac Ac o 16 S11c2 A AcB Bc Bc B Ac x 16 S12c2 A Ac Bc B Bc B Ac A A

TABLE 6 # of base Sub-sequence # of base Sub-sequence sequence Indexarrangement sequence Index arrangement 4 S2 A B 4 S2 A B o 6 A B Ac O 6A B Bc x 8 S21 A B Ac Bc O 8 S22 A B Bc Ac O 12 S211 A B Ac Bc A Ac O 12S221 A B Bc Ac A Ac X 16 S2111 A B Ac Bc A Ac B X 16 S2211 A B Bc Ac AAc B Bc Bc X 16 S2112 A B Ac Bc A Ac Bc X 16 S2212 A B Bc Ac A Ac Bc B BX 12 S212 A B Ac Bc A B X 12 S222 A B Bc Ac A B X 16 S2121 A B Ac Bc A BAc X 16 S2221 A B Bc Ac A B Ac Bc Bc X 16 S2122 A B Ac Bc A B Bc X 16S2222 A B Bc Ac A B Bc Ac Ac O 12 S213 A B Ac Bc A Bc O 12 S223 A B BcAc A Bc X 16 S2131 A B Ac Bc A Bc Ac X 16 S2231 A B Bc Ac A Bc Ac B B X16 S2132 A B Ac Bc A Bc B X 16 S2232 A B Bc Ac A Bc B Ac Ac X 12 S214 AB Ac Bc Ac A O 12 S224 A B Bc Ac Ac A X 16 S2141 A B Ac Bc Ac A B X 16S2241 A B Bc Ac Ac A B Bc Bc X 16 S2142 A B Ac Bc Ac A Bc O 16 S2242 A BBc Ac Ac A Bc A B O 12 S215 A B Ac Bc Ac B O 12 S225 A B Bc Ac Ac B X 16S2151 A B Ac Bc Ac B A O 16 S2251 A B Bc Ac Ac B A Bc Bc X 16 S2152 A BAc Bc Ac B Bc X 16 S2252 A B Bc Ac Ac B Bc A A X 12 S216 A B Ac Bc Ac BcO 12 S226 A B Bc Ac Ac Bc X 16 S2162 A B Ac Bc Ac Bc A X 16 S2261 A B BcAc Ac Bc A B B X 16 S2162 A B Ac Bc Ac Bc B O 16 S2262 A B Bc Ac Ac Bc BA A O 12 S217 A B Ac Bc B A X 12 S227 A B Bc Ac B A X 16 S2171 A B Ac BcB A Ac X 16 S2271 A B Bc Ac B A Ac Bc Bc X 16 S2172 A B Ac Bc B A Bc X16 S2272 A B Bc Ac B A Bc Ac Ac X 12 S218 A B Ac Bc B Ac O 12 S228 A BBc Ac B Ac X 16 S2181 A B Ac Bc B Ac A O 16 S2281 A B Bc Ac B Ac A Bc BcX 16 S2182 A B Ac Bc B Ac Bc O 16 S2282 A B Bc Ac B Ac Bc A A O 12 S219A B Ac Bc B Bc X 12 S229 A B Bc Ac B Bc O 16 S2191 A B Ac Bc B Bc A X 16S2291 A B Bc Ac B Bc A Ac Ac O 16 S2192 A B Ac Bc B Bc Ac X 16 S2292 A BBc Ac B Bc Ac A A O 12 S21a A B Ac Bc Bc A O 12 S22a A B Bc Ac Bc A O 16S21a1 A B Ac Bc Bc A Ac X 16 S22a1 A B Bc Ac Bc A Ac B B X 16 S21a2 A BAc Bc Bc A B X 16 S22a2 A B Bc Ac Bc A B Ac Ac O 12 S21b A B Ac Bc Bc AcX 12 S22b A B Bc Ac Bc Ac X 16 S21b1 A B Ac Bc Bc Ac A X 16 S22b1 A B BcAc Bc Ac A B B O 16 S21b2 A B Ac Bc Bc Ac B X 16 S22b2 A B Bc Ac Bc Ac BA A O 12 S21c A B Ac Bc Bc B O 12 S22c A B Bc Ac Bc B O 16 S21c1 A B AcBc Bc B A X 16 S22c1 A B Bc Ac Bc B A Ac Ac X 16 S21c2 A B Ac Bc Bc B AcO 16 S22c2 A B Bc Ac Bc B Ac A A

TABLE 7 # of base Sub-sequence # of base Sub-sequence sequence Indexarrangement sequence Index arrangement 4 S3 A Bc 4 S3 A Bc O 6 A Bc Ac O6 S32_6 A Bc B O 8 S31 A Bc Ac B O 8 S32 A Bc B Ac O 12 S311 A Bc Ac B AAc O 12 S321 A Bc B Ac A Ac X 16 S3111 A Bc Ac B A Ac B X 16 S3211 A BcB Ac A Ac B Bc Bc X 16 S3112 A Bc Ac B A Ac Bc X 16 S3212 A Bc B Ac A AcBc B B O 12 S312 A Bc Ac B A B O 12 S322 A Bc B Ac A B X 16 S3121 A BcAc B A B Ac X 16 S3221 A Bc B Ac A B Ac Bc Bc X 16 S3122 A Bc Ac B A BBc X 16 S3222 A Bc B Ac A B Bc Ac Ac X 12 S313 A Bc Ac B A Bc X 12 S323A Bc B Ac A Bc X X 16 S3231 A Bc B Ac A Bc Ac B X X 16 S3232 A Bc B Ac ABc B Ac O 12 S314 A Bc Ac B Ac A O 12 S324 A Bc B Ac Ac A X 16 S3141 ABc Ac B Ac A B O 16 S3241 A Bc B Ac Ac A B Bc Bc X 16 S3142 A Bc Ac B AcA Bc X 16 S3242 A Bc B Ac Ac A Bc B B X 12 S315 A Bc Ac B Ac B O 12 S325A Bc B Ac Ac B X X 16 S3251 A Bc B Ac Ac B A Bc X O 16 S3252 A Bc B AcAc B Bc A O 12 S316 A Bc Ac B Ac Bc O 12 S326 A Bc B Ac Ac Bc X 16 S3161A Bc Ac B Ac Bc A O 16 S3261 A Bc B Ac Ac Bc A B B X 16 S3162 A Bc Ac BAc Bc B X 16 S3262 A Bc B Ac Ac Bc B A A O 12 S317 A Bc Ac B B A O 12S327 A Bc B Ac B A O 16 S3171 A Bc Ac B B A Ac O 16 S3271 A Bc B Ac B AAc Bc Bc X 16 S3172 A Bc Ac B B A Bc X 16 S3272 A Bc B Ac B A Bc Ac Ac O12 S318 A Bc Ac B B Ac X 12 S328 A Bc B Ac B Ac X 16 S3181 A Bc Ac B BAc A X 16 S3281 A Bc B Ac B Ac A Bc Bc O 16 S3182 A Bc Ac B B Ac Bc X 16S3282 A Bc B Ac B Ac Bc A A O 12 S319 A Bc Ac B B Bc O 12 S329 A Bc B AcB Bc O 16 S3191 A Bc Ac B B Bc A X 16 S3291 A Bc B Ac B Bc A Ac Ac X 16S3192 A Bc Ac B B Bc Ac X 16 S3292 A Bc B Ac B Bc Ac A A O 12 S31a A BcAc B Bc A O 12 S32a A Bc B Ac Bc A X 16 S31a1 A Bc Ac B Bc A B X 16S32a1 A Bc B Ac Bc A B Ac Ac X 16 S31a2 A Bc Ac B Bc A Ac X 16 S32a2 ABc B Ac Bc A Ac B B X 12 S31b A Bc Ac B Bc Ac O 12 S32b A Bc B Ac Bc AcX 16 S31b1 A Bc Ac B Bc Ac A X 16 S32b1 A Bc B Ac Bc Ac A B B X 16 S31b2A Bc Ac B Bc Ac B O 16 S32b2 A Bc B Ac Bc Ac B A A O 12 S31c A Bc Ac BBc B X 12 S32c A Bc B Ac Bc B O 16 S31c1 A Bc Ac B Bc B A X 16 S32c1 ABc B Ac Bc B A Ac Ac O 16 S31c2 A Bc Ac B Bc B Ac X 16 S32c2 A Bc B AcBc B Ac A A

In the case of a length-N sequence, a part of the sequence,specifically, a portion with a length of L, may be used depending onsituations. Sequences with good auto-correlation properties regardlessof lengths are listed in the following description.

Table 8 below shows sequences, each consisting of six or eightsub-sequences on the basis of (A Ac Bc B).

TABLE 8 S1252 = [A Ac Bc B Ac B Bc A] S1272 = [A Ac Bc B B A Bc Ac]S1281 = [A Ac Bc B B Ac A Bc] S1292 = [A Ac Bc B B Bc Ac A] S12a2 = [AAc Bc B Bc A B Ac] S123 = [A Ac Bc B A Bc] S124 = [A Ac Bc B Ac A] S12b= [A Ac Bc B Bc Ac]

Table 9 below shows sequences, each consisting of six or eightsub-sequences on the basis of (A B Bc Ac).

TABLE 9 S2242 = [A B Bc Ac Ac A Bc B] S2251 = [A B Bc Ac Ac B A Bc]S2262 = [A B Bc Ac Ac Bc B A] S2281 = [A B Bc Ac B Ac A Bc] S2282 = [A BBc Ac B Ac Bc A] S22c2 = [A B Bc Ac Bc B Ac A] S221 = [A B Bc Ac A Ac]S223 = [A B Bc Ac A Bc] S22a = [A B Bc Ac Bc A]

Table 10 below shows sequences, each consisting of six or eightsub-sequences on the basis of (A Bc Ac B).

TABLE 10 S3171 = [A Bc Ac B B A Ac Bc] S3182 = [A Bc Ac B B Ac Bc A]S3191 = [A Bc Ac B B Bc A Ac] S31c1 = [A Bc Ac B Bc B A Ac] S31c2 = [ABc Ac B Bc B Ac A] S311 = [A Bc Ac B A Ac] S312 = [A Bc Ac B A B] S314 =[A Bc Ac B Ac A] S316 = [A Bc Ac B Ac Bc] S31a = [A Bc Ac B Bc A]

Table 11 below shows sequences, each consisting of six or eightsub-sequences on the basis of (A Bc B Ac).

TABLE 11 S3241 = [A Bc B Ac Ac A B Bc] S3252 = [A Bc B Ac Ac B Bc A]S3261 = [A Bc B Ac Ac Bc A B] S3271 = [A Bc B Ac B A Ac Bc] S32b2 = [ABc B Ac Bc Ac B A] S321 = [A Bc B Ac A Ac] S322 = [A Bc B Ac A B] S329 =[A Bc B Ac B Bc] S32a = [A Bc B Ac Bc A]

The above sequences consisting of six or eight sub-sequences on thebasis of the four sub-sequences, for example, (A Ac Bc B), (A B Bc Ac),(A Bc Ac B), or (A Bc B Ac) show good auto-correlation properties evenif only L elements are used.

Embodiment 2—A Case in which Set 2 is Used

Similar to embodiment 1, in this embodiment, configuration methods canbe defined as follows according to the number of sub-sequencesconstituting a long-length sequence.

(1) A Configuration Method Using Two Sub-Sequences

A random sub-sequence is selected as the first sub-sequence, and asub-sequence different from the first sub-sequence can be selected asthe second sub-sequence. The priority for selecting the secondsub-sequence from among candidates is as follows.

Priority 1. A sub-sequence having an OCC different from that of thefirst sub-sequence and the same base sequence arrangement as that of thefirst sub-sequence is selected.

Priority 2. A sub-sequence having an OCC and a base sequence arrangementdifferent from those of the first sub-sequence is selected.

Priority 3. A sub-sequence with the same OCC as that of the firstsub-sequence and a base sequence arrangement different from that of thefirst sub-sequence is selected.

Table 12 below shows an example of using two sub-sequences.

TABLE 12 Sub-sequence arrangement Sequence Auto-correlation result C Cc(an bn an −bn) 0 0 0 4 C Dc (an bn bn −an) 1 0 1 4 C D (an bn bn an) 1 01 4

(2) A Configuration Method Using Four Sub-Sequences

The third sub-sequence can be selected from among the remainingsub-sequences, which are not selected in the previous process, accordingto the following priority.

Priority 1. A sub-sequence having the same OCC and base sequencearrangement as those of the first sub-sequence is selected.

Priority 2. A sub-sequence having an OCC and a base sequence arrangementdifferent from those of the first sub-sequence is selected.

Priority 3. A sub-sequence having an OCC different from that of thefirst sub-sequence and the same base sequence arrangement as that of thefirst sub-sequence is selected.

Table 13 below shows an example of using three sub-sequences.

TABLE 13 Sub-sequence arrangement Sequence Auto-correlation result C CcDc (an bn an −bn bn −an) 1 0 0 0 1 6 C Cc D (an bn an −bn bn an) 1 0 2 01 6 C Dc Cc (an bn bn −an an bn) 0 2 0 0 0 6 C Dc D (an bn bn −an bn an)1 0 0 0 1 6 C D Cc (an bn bn an an −bn) 0 0 0 0 2 6 C D Dc (an bn bn anbn −an) 1 0 2 0 1 6

In this case, the remaining sub-sequence which is not selected in theprevious process can be configured as the fourth sub-sequence.

TABLE 14 Sub-sequence arrangement Sequence Auto-correlation result C CcDc D (an bn an −bn bn −an bn an) 1 0 1 0 1 0 1 8 C Cc D Dc (an bn an −bnbn an bn −an) 1 0 1 0 1 0 1 8 C Dc Cc D (an bn bn −an an −bn bn an) 1 01 0 1 0 1 8 C Dc D Cc (an bn bn −an bn an an −bn) 0 0 0 0 2 0 2 8 C D CcDc (an bn bn an an −bn bn −an) 1 0 1 0 1 0 0 8 C D Dc Cc (an bn bn an bn−an an −bn) 0 0 2 0 2 0 0 8

(3) A Configuration Method Using Eight Sub-Sequences

The configuration method using up to eight sub-sequences according tothe aforementioned principles is as follows.

<Example of Using Five Sub-Sequences>

S1=[C Cc D Dc Cc]; O

S2=[C Cc D Dc D]; O

S3=[C D Cc Dc Cc];

S4=[C D Cc Dc D];

S5=[C Cc D Dc A]; O

S6=[C Cc D Dc mB]; O

S7=[C D Cc Dc A];

S8=[C D Cc mB mB];

<Example of Using Six Sub-Sequences>

S1=[A mA B mB A mA];

S2=[A mA B mB mA A]; O

S3=[A mA B mB A B];

S4=[A mA B mB A mB]; O

S5=[A mA B mB A A];

S6=[A mA B mB mA mA]; O

S7=[A mA B mB mA B];

S8=[A mA B mB mA mB];

S9=[A mA B mB B A]; O

S10=[A mA B mB B mA]; O

S11=[A mA B mB B B];

S12=[A mA B mB B mB];

S13=[A mA B mB mB A];

S14=[A mA B mB mB mA]; O

S15=[A mA B mB mB B]; O

S16=[A mA B mB mB mB];

S17=[A B mA mB A B];

S18=[A B mA mB A mB]; O

S19=[A B mA mB mA B];

S20=[A B mA mB mA mB]; O

S21=[A B mA mB A A];

S22=[A B mA mB A mA]; O

S23=[A B mA mB mA A];

S24=[A B mA mB mA mA];

S25=[A B mA mB B A];

S26=[A B mA mB B mA];

S27=[A B mA mB B B]; O

S28=[A B mA mB B mB];

S29=[A B mA mB mB A]; O

S30=[A B mA mB mB mA];

S31=[A B mA mB mB B]; O

S32=[A B mA mB mB mB];

Hereinafter, a case where the above-described long-length sequence isused for NB IoT synchronization signals will be described.

Application to NB-IoT

As described above, NB-IoT has system bandwidth (BW) corresponding toone PRB of the LTE system and supports low complexity and low powerconsumption. To this end, this may be mainly used as a communicationsystem for implementing IoT by supporting a machine-type communication(MTC) device in a cellular system. Since the NB-LTE system use the sameOFDM parameters including subcarrier spacing as in the conventional LTEsystem, one PRB in the legacy LTE band is allocated for the NB-LTEwithout allocation of additional bands. That is, the NB-LTE system hasadvantages in that frequencies can be efficiently used.

Hereinafter, a method of transmitting an NB-PSS and an NB-SSS will bedescribed in detail based on the above description.

NB-PSS Transmission

FIG. 9 is a diagram illustrating in detail a method for transmitting anNB-PSS through repetition in a plurality of OFDM symbols.

As described above, the NB-PSS is transmitted using a plurality of OFDMsymbols. At this time, it is proposed that the same sequence isrepeatedly transmitted in the OFDM symbols, and each OFDM symbol ismultiplied by a specific cover sequence as shown in FIG. 9.

Assuming that the system bandwidth is one PRB and subcarrier spacing is15 kHz, the maximum length of a sequence which may be transmitted in oneOFDM symbol is 12. For convenience of description, it is assumed thatthe system bandwidth of the NB-LTE system is on PRB and the subcarrierspacing is 15 kHz.

The PSS is generally detected by a receiver in the time domain inconsideration of computational complexity. In the PSS, in order toacquire time/frequency synchronization, a sliding window is applied to aPSS sequence to perform correlation. In the PSS transmission structureshown in FIG. 9, since the same sequence is transmitted in every OFDMsymbol, a relatively large correlation value can be obtained in a periodcorresponding to the OFDM symbol length. If the condition of acomplementary Golay sequence is used, the period during which therelatively large correlation value is outputted can be increased,thereby improving correlation properties.

In addition, if the cover sequence is applied to every OFDM symbol asshown in FIG. 9, the correlation properties can be further improved. Totransmit the PSS using a complementary Golay sequence, the followingmethods can be used.

Method 1: A method of alternately arranging a pair of complementaryGolay sequences in OFDM symbols.

For example, assuming that N=6 OFDM symbols, a(n) is transmitted in OFDMsymbol 1 and b(n) is transmitted in OFDM symbol 2. In this case, c(n)can be applied by taking length-6 of a length-7 m-sequence. At thistime, it is preferable that the number of OFDM symbols for transmittingthe PSS is an even number. If it is assumed that complementary Golaysequences are binary sequences, a possible sequence length is2^(a)10^(b)26^(c) (where each of a, b and c is an integer equal to orgreater than 0). If one OFDM symbol has twelve available resources, thepossible Golay sequence length may be 10. For example, a pair oflength-10 complement Golay sequences is a(n)=[1 1−1 −1 1 1 1−1 1−1] andb(n)=[1 1 1 1 1 −1 1 −1 −1 1]. In addition, the REs of the OFDM symbols,where the sequence is not allocated, are filled with 0 and thentransmitted. If a non-binary complementary Golay sequence is assumed,since a sequence pair is present without length limit, a pair oflength-12 sequences a(n) and b(n) may be transmitted in the OFDM symbolsin the same manner.

FIG. 10 is a diagram illustrating correlation properties of a pair oflength-10 complementary sequences a(n) and b(n) and various c(n)patterns.

As another method, if the PSS is transmitted in an odd number of OFDMsymbols, the PSS may be transmitted such that one sequence of thesequence pair is transmitted once more. For example, in the case of N=7OFDM symbols, the sequences may be arranged in the following order: a(n)b(n) a(n) b(n) a(n) b(n) a(n) and then transmitted in the OFDM symbols.

Method 2: A method of arranging a pair of complementary Golay sequencesin one OFDM symbol.

Method 2-1: A method of generating and arranging a sequencecorresponding to ½ of one OFDM symbol.

For example, assuming that N=6 OFDM symbols, length-6 non-binarycomplementary Golay sequences a(n) and b(n) are generated, a(n) isallocated to half of available REs in one OFDM symbol, and b(n) isallocated to the remaining half. In this case, the RE allocation may beperformed such that a(n) is allocated first to the first half and b(n)is allocated to the remaining half.

Method 2-2: A method of superpositioning and transmitting a(n) and b(n)in one OFDM symbol.

For example, assuming that N=6 OFDM symbols, it is possible to generatelength-10/12 binary/non-binary complementary Golay sequences andcalculate a(n)+b(n) for transmission thereof.

Method 3: A method of arranging and transmitting L (L>2) or morecomplementary Golay sequences.

In this case, the number of OFDM symbols for transmitting the PSS shouldsatisfy the requirement of multiples of L. For example, in the case ofL=3 and N=6, the length-10 or length-12 complementary Golay sequencesla(n), lb(n), lc(n) can be sequentially arranged and transmitted in theOFDM symbols. That is, the sequences are arranged in the followingorder: la(n), lb(n), lc(n), la(n), lb(n), lc(n) and then transmittedafter applying a cover sequence c(n).

Meanwhile, in the above-described NB-PSS transmission method, a ZCsequence having elements corresponding in number to 12 subcarriers maybe used in the frequency domain of one OFDM symbol. In this case, only11 subcarriers can be used to prevent the NB-PSS from being mapped to aDC element. Therefore, a length-11 ZC sequence may be used.

As a particular example of the above-described NB-PSS transmissionmethod, it is possible to generate the sequence d₁(n) of the NB-PSSusing the length-11 ZC sequence in the frequency domain as shown inEquation 8.

$\begin{matrix}{{{d_{l}(n)} = {{S(l)} \cdot e^{{- j}\frac{\pi\;{{un}{({n + 1})}}}{11}}}},{n = 0},1,\ldots\mspace{14mu},10} & \lbrack {{Equation}\mspace{14mu} 8} \rbrack\end{matrix}$

In Equation 8, it is preferable to specify the root index u of the ZCsequence as a specific root index as described above. Although thepresent embodiment assumes that u=5, the invention is not limitedthereto.

In addition, in Equation 8, s(l) denotes the above-described coversequence, and S(l) can be defined according to the OFDM symbol index ‘1’as shown in Table 15.

TABLE 15 Cyclic prefix length S(3), . . . , S(13) Normal 1 1 1 1 −1 −1 11 1 −1 1

NB-SSS Transmission

Since the NB-PSS is transmitted using one specific sequence as describedabove, it is required to represent 504 NB cell identities using theNB-SSS. Therefore, a method for transmitting the NB-SSS in a pluralityof OFDM symbols similar to the NB-PSS and mapping a long sequence to theplurality of OFDM symbols in order to distinguish between the cellidentities is proposed.

FIG. 11 is a diagram illustrating the concept of NB-SSS transmissionaccording to an embodiment of the present invention.

By detecting an SSS, a receiving device, that is, UE, may obtaininformation on cell id detection, information on the index of a subframecarrying the SSS, and other system information. To transmit the SSS, itis preferable to use a long length-M sequence over a plurality of OFDMsymbols as shown in FIG. 11, instead of repeatedly performingtransmission using a plurality of OFDM symbols similar to theabove-described PSS.

Thus, a long-length sequence to be used for the NB-SSS may be configuredby a combination of sub-sequences selected in consideration ofauto-correlation properties.

Referring to FIG. 11, a length-M sequence can be generated and thenmultiplied by a length-M scrambling sequence in each element.Specifically, the length-M sequence is divided into length-L (M>=L)sequences, the length-L sequences are mapped to N OFDM symbols, and thena scrambling sequence s(n) is applied. By doing so, the length-Msequence is transmitted in the N OFDM symbols. For example, assumingthat M=72, L=12 and N=6, a length-72 sequence is divided into sixlength-12 sequences, and the length-12 sequences are respectivelytransmitted in six OFDM symbols. The above-described numerical valuesare exemplary, and the values may be changed as long as M=L*N issatisfied.

In this case, an SSS sequence can be designed as follows to transmitcorresponding information.

In the legacy LTE system, 504 physical cell IDs are indicated by a PSSand an SSS. On the other hand, in the NB-IoT system, 504 physical cellIDs are indicated by an NB-SSS. In the legacy LTE system, a PBCH istransmitted every 10 ms, and a PSS/SSS is transmitted every 5 ms. Thatis, the PSS/SSS is transmitted twice during the PBCH transmissionperiod. Thus, an SSS transmission subframe number needs to be indicatedby the SSS, and to indicate the subframe index, SSS1 and SSS2 consistingof the SSS are swapped according to subframe positions. Considering thatin the NB-IoT system, an NB-PBCH is transmitted with a period of 80 msand the NB-PSS is transmitted with a period of 10 ms, the NB-SSS can bedesigned to be transmitted with a period longer than that of the NB-PSS(e.g., 20 ms or 40 ms). If the NB-SSS transmission period is designed tobe shorter than the NB-PBCH transmission period, i.e., 80 ms, the numberof candidate positions capable of transmitting the NB-SSS during theNB-PBCH transmission period may be greater than that of the LTE system

In summary, the NB-SSS should include a significantly large amount ofinformation including not only a cell-ID but also an NB-SSS frame index.Therefore, the NB-SSS capable of simplifying reception complexity of aUE while containing a large amount of information needs to be designed.

To this end, in addition to the method of transmitting a long sequencein a plurality of OFDM symbols as described with reference to FIG. 11,it is proposed in an embodiment of the present invention to configurethe NB-SSS using combinations of multiple sequences. Specifically, theNB-SSS may be configured by combining a base-sequence, a scramblingsequence, a cyclic shift and a cover sequence. For example, abase-sequence may be generated using an L-length ZC sequence, and thenelement-wise multiplication may be applied to an L-length scramblingsequence. Thereafter, a cyclic shift is performed, and then element-wisemultiplication is applied after generation of an L-length coversequence.

FIG. 12 is a diagram illustrating a method for generating andtransmitting an NB-SSS according to an embodiment of the presentinvention.

Referring to FIG. 12 a length-M ZC sequence can be generated first.

$\begin{matrix}{{{{Szc}( {u,n} )} = e^{j\frac{\pi\;{{un}{({n + 1})}}}{M}}},{where},{u\text{:}\mspace{14mu}{root}\mspace{14mu}{index}},{n\text{:}\mspace{14mu}{sequence}\mspace{14mu}{index}}} & \lbrack {{Equation}\mspace{14mu} 9} \rbrack\end{matrix}$

It is assumed that this ZC sequence is long enough to transmit theNB-SSS in a plurality of OFDM symbols as described above. In the presentembodiment, M=132 (12 subcarriers*11 OFDM symbols). Here, eleven OFDMsymbols may be obtained by subtracting three OFDM symbols, in which aPDCCH can be transmitted, from fourteen OFDM symbols included in onesubframe, as described above regarding the NB-PSS. However, the numberof OFDM symbols may vary according to system implementation.

As well known to the public, in the case of a ZC sequence, root indicescan be identified when the sequence length is a prime number. Therefore,as described above, it is preferable to use 131, which is the largestprime number less than 132, as the ZC sequence length rather than alength-132 ZC sequence and then cyclically extend a length-131 ZCsequence to a length-132 ZC sequence as shown in Equation 10.

$\begin{matrix}{{{{{Szc}( {u,n} )} = e^{j\frac{\pi\;{{un}^{\prime}{({n^{\prime} + 1})}}}{M}}},{where},{u\text{:}\mspace{14mu}{root}\mspace{14mu}{index}},{n = 0},1,\ldots\mspace{14mu},M}{n^{\prime} = {n\mspace{14mu}{mod}\mspace{14mu} M}}} & \lbrack {{Equation}\mspace{14mu} 10} \rbrack\end{matrix}$

Since the NB-LTE system uses one specific sequence as the NB-PSS asdescribed above, 504 cell IDs need to be identified by the NB-SSS, andthus the length-131 ZC sequence is insufficient to indicate the 504 cellIDs.

To this end, in an embodiment of the present invention, it is proposedthat as shown in FIG. 12, the ZC sequence is multiplied by a length-Mcover sequence in each element and this cover sequence is configured toindicate a predetermined number of offsets or position indices so thatthe resultant NB-SSS indicates all cell IDs. For example, at least fouroffsets are required to represent the 504 cell IDs. Accordingly, in apreferred embodiment of the present invention, it is proposed to limitthe number of root indices of the ZC sequence to be less than the lengthof M (131) and distinguishes between the 504 (=126*4) cell IDs throughthe cover sequence multiplied by the ZC sequence in each element.

Meanwhile, FIG. 12 shows that the length-M cover sequence is used toinform the position of the NB-SSS. The NB-SSS may be transmitted lessfrequently than the NB-PSS as described above, and thus signaling forindicating this may be required. Information on the position where theNB-SSS will be transmitted can be informed through the NB-SSS itselfusing not only the method of transmitting the information through thecover sequence as shown in FIG. 9 but also the cyclic shift applied tothe ZC sequence as described above. In some cases, the above-describedoffset can be applied to the ZC sequence instead of the cover sequence.

As mentioned in the foregoing description, 131 root indices can beselected in the case of the length-131 ZC sequence. However, when fouroffsets are used to indicate the 504 cell IDs, root indices showing goodperformance among the 131 root indices can be used because 126 rootindices are selected from among the 131 root indices.

FIG. 13 is diagram illustrating a method for selecting root indices of aZC sequence to be used for an NB-SSS according to an embodiment of thepresent invention.

If a long single ZC sequence is used upon configuring the NB-SSS, a PAPRmay increase in spite of using the ZC sequence. In this case, the PAPRof the NB-SSS varies depending root indices. In particular, low rootindices (high root indices paired therewith) and middle root indices maygenerate a high PAPR.

A variety of combinations can be considered to represent the 504 PCIDs.For example, 126 root indices×4 additional indices, 84 root indices×6additional indices, 42 root indices×12 additional indices, etc. may beconsidered.

In the length-131 ZC sequence, root indices 1, 130, 2, 129, 3, 128, 65,66, 64, 67, etc. generate high PAPR. Specifically, FIG. 10 (a) shows acase where root indices causing high PAPRs are used, and FIG. 10 (b)shows a case where root indices indicating low PAPRs are used.

If 126 root indices are used, four root indices are excluded from rootindices 1 to 130. Thus, a preferred embodiment of the present inventionproposes to use indices 3 to 128 except root indices which cause highPAPRs. In this case, the average PAPR may be decreased. That is, in thepresent embodiment, it is proposed to select root indices of thelength-L ZC sequence used to transmit the NB-SSS from among M rootindices (where M is smaller than L) and select the M root indices from arange of [k, M+k−1] using a predetermined offset, k rather than a rangeof [0, M−1]. In addition, it is also proposed to select the ZC sequenceas one among 126 root indices from a range of [3, 128].

The above description will be summarized as follows.

In the NB-LTE system, an NB-SSS can be transmitted with a period of 20ms. This NB-SSS may indicate not only 504 PCIDs but also a specificposition in a range of 80 ms, where transmission is performed.

In addition, the NB-SSS sequence is generated using a length-131frequency-domain ZC sequence. In this case, root indices may be selectedfrom a range of [3, 128]. Thereafter, a cyclic shift is applied to thisZC sequence, and then it is multiplied by a binary scrambling sequencein each element. In this structure, the 504 PCIDs can be represented by126 ZC root indices and four binary scrambling sequences. In addition,the position of the NB-SSS in the range of 80 ms can be represented byfour cyclic shift values (e.g., 0, 33, 66 and 99).

In this case, the Hadamard sequence shown in Equation 11 can be used asthe binary scrambling sequence corresponding to a cover sequence.b _(q)(n)=Hadamard₂ _(q) ⁻¹ ^(128×128)(mod(n,128)),q=0,1,2,3[Equation11]

When the Hadamard sequence is used, the NB-SSS can be configured asfollows.

$\begin{matrix}{{{SSSu},q,{{k(n)} = {{{Su}(n)}*{{bq}(n)}*{{Ck}(n)}}}}{{{{Su}(n)} = e^{j\frac{{\pi{({u + 3})}}{n{({n + 1})}}}{131}}},{n = 0},\ldots\mspace{14mu},131,{u = 0},\ldots\mspace{14mu},125}{{{{bq}(n)} = {{Hadamard}_{2^{q} - 1}^{128 \times 128}( {{mod}( {n,128} )} )}},{n = 0},\ldots\mspace{14mu},131,{q = 0},1,2,3}{{{C_{k}(n\;)} = e^{{- j}\frac{2\;\pi\; 33{kn}}{132}}},{n = 0},\ldots\mspace{14mu},131,{k = 0},1,2,3}{{u = {{mod}( {{PCID},126} )}},{q = \lfloor \frac{PCID}{126} \rfloor},{k = {{Subframe}\mspace{14mu}{indication}}}}} & \lbrack {{Equation}\mspace{14mu} 12} \rbrack\end{matrix}$

Hereinafter, a description will be given of how the Hadamard sequence isapplied to the above-described structure.

FIG. 14 is a diagram illustrating cross-correlation values when aspecific Hadamard sequence is used for an NB-SSS according to anembodiment of the present invention.

As shown in FIG. 14, if there is a sequence having the same time-domaincyclic shift as that of the Hadamard sequence (e.g., [1 1 1 1 . . . ],[1 −1 1−1 . . . ]), it may show poor cross-correlation properties.

To solve this problem, an embodiment of the present invention proposesthat when four sequences are selected from the Hadamard sequences, thesequences which are not included in a time-domain cyclic shift will beused. For example, if [1 1 1 1 . . . ], [1 −1 1 −1 . . . ], etc. areincluded in the time-domain cyclic shift, 1 and 2 of a Hadamard matrixare excluded because they are sequences composed of [1 1 1 1 . . . ] [1−1 1 −1 . . . ]. In this case, if q=0, 1, 2, or 3, it is preferable toselect an N (>=4) times multiple of q.

$\begin{matrix}{{{SSSu},q,{{k(n)} = {{{Su}(n)}*{{bq}(n)}*{{Ck}(n)}}}}{{{{Su}(n)} = e^{j\frac{{\pi{({u + 3})}}{n{({n + 1})}}}{131}}},{n = 0},\ldots\mspace{14mu},131,{u = 0},\ldots\mspace{14mu},125}{{{{bq}(n)} = {{Hadamard}_{5q}^{128 \times 128}( {{mod}( {n,128} )} )}},{n = 0},\ldots\mspace{14mu},131,{q = 0},1,2,3}{{{C_{k}(n\;)} = e^{{- j}\frac{2\;\pi\; 33{kn}}{132}}},{n = 0},\ldots\mspace{14mu},131,{k = 0},1,2,3}{{u = {{mod}( {{PCID},126} )}},{q = \lfloor \frac{PCID}{126} \rfloor},{k = {{Subframe}\mspace{14mu}{indication}}}}} & \lbrack {{Equation}\mspace{14mu} 13} \rbrack\end{matrix}$

According to another embodiment of the present invention, a binaryHadamard sequence is configured.

If a time-domain cyclic shift is configured with a complex value, it ispossible to generate a sequence existing in a domain different from thatof the Hadamard sequence, thereby eliminating ambiguity between the twosequences. For example, if a time-domain cyclic shift is configured withoffsets different from 33 offsets in 132 samples, a sequence may have acomplex value. Time-domain shift values capable of maintaining an equaldistance possible in a length-132 sequence are 32, 34, etc. In addition,36 offsets can also be assumed.

If the Hadamard sequence and time-domain cyclic shift are configured indifferent domains, a full orthogonal sequence or a quasi-orthogonalsequence can be applied as the Hadamard sequence.

If the Hadamard matrix is cyclically extended from 128 to 132, sequenceswith q=0, 1, 2 and 3 become fully orthogonal to each other.

Equations below are examples according to the embodiments. In additionto the following examples, there are various examples which satisfy theabove-described principles.

$\begin{matrix}{{{SSSu},q,{{k(n)} = {{{Su}(n)}*{{bq}(n)}*{{Ck}(n)}}}}{{{{Su}(n)} = e^{j\frac{{\pi{({u + 3})}}{n{({n + 1})}}}{131}}},{n = 0},\ldots\mspace{14mu},131,{u = 0},\ldots\mspace{14mu},125}{{{{bq}(n)} = {{Hadamard}_{q}^{128 \times 128}( {{mod}( {n,128} )} )}},{n = 0},\ldots\mspace{14mu},131,{q = 0},1,2,3}{{{C_{k}(n\;)} = e^{{- j}\frac{2\;\pi\; 32{kn}}{132}}},{n = 0},\ldots\mspace{14mu},131,{k = 0},1,2,3}{{u = {{mod}( {{PCID},126} )}},{q = \lfloor \frac{PCID}{126} \rfloor},{k = {{Subframe}\mspace{14mu}{indication}}}}} & \lbrack {{Equation}\mspace{14mu} 14} \rbrack \\{{{SSSu},q,{{k(n)} = {{{Su}(n)}*{{bq}(n)}*{{Ck}(n)}}}}{{{{Su}(n)} = e^{j\frac{{\pi{({u + 3})}}{n{({n + 1})}}}{131}}},{n = 0},\ldots\mspace{14mu},131,{u = 0},\ldots\mspace{14mu},125}{{{{bq}(n)} = {{Hadamard}_{2^{q} - 1}^{128 \times 128}( {{mod}( {n,128} )} )}},{n = 0},\ldots\mspace{14mu},131,{q = 0},1,2,3}{{{C_{k}(n\;)} = e^{{- j}\frac{2\;\pi\; 32{kn}}{132}}},{n = 0},\ldots\mspace{14mu},131,{k = 0},1,2,3}{{u = {{mod}( {{PCID},126} )}},{q = \lfloor \frac{PCID}{126} \rfloor},{k = {{Subframe}\mspace{14mu}{indication}}}}} & \lbrack {{Equation}\mspace{14mu} 15} \rbrack \\{{{SSSu},q,{{k(n)} = {{{Su}(n)}*{{bq}(n)}*{{Ck}(n)}}}}{{{{Su}(n)} = e^{j\frac{{\pi{({u + 3})}}{n{({n + 1})}}}{131}}},{n = 0},\ldots\mspace{14mu},131,{u = 0},\ldots\mspace{14mu},125}{{{{bq}(n)} = {{Hadamard}_{2^{q} - 1}^{128 \times 128}( {{mod}( {n,128} )} )}},{n = 0},\ldots\mspace{14mu},131,{q = 0},1,2,3}{{{C_{k}(n\;)} = e^{{- j}\frac{2\;\pi\; 36{kn}}{132}}},{n = 0},\ldots\mspace{14mu},131,{k = 0},1,2,3}{{u = {{mod}( {{PCID},126} )}},{q = \lfloor \frac{PCID}{126} \rfloor},{k = {{Subframe}\mspace{14mu}{indication}}}}} & \lbrack {{Equation}\mspace{14mu} 16} \rbrack \\{{{SSSu},q,{{k(n)} = {{{Su}(n)}*{{bq}(n)}*{{Ck}(n)}}}}{{{{Su}(n)} = e^{j\frac{{\pi{({u + 3})}}{n{({n + 1})}}}{131}}},{n = 0},\ldots\mspace{14mu},131,{u = 0},\ldots\mspace{14mu},125}{{{{bq}(n)} = {{Hadamard}_{q}^{128 \times 128}( {{mod}( {n,128} )} )}},{n = 0},\ldots\mspace{14mu},131,{q = 0},1,2,3}{{{C_{k}(n\;)} = e^{{- j}\frac{2\;\pi\; 36{kn}}{132}}},{n = 0},\ldots\mspace{14mu},131,{k = 0},1,2,3}{{u = {{mod}( {{PCID},126} )}},{q = \lfloor \frac{PCID}{126} \rfloor},{k = {{Subframe}\mspace{14mu}{indication}}}}} & \lbrack {{Equation}\mspace{14mu} 17} \rbrack \\{{{SSSu},q,{{k(n)} = {{{Su}(n)}*{{bq}(n)}*{{Ck}(n)}}}}{{{{Su}(n)} = e^{j\frac{{\pi{({u + 3})}}{n{({n + 1})}}}{131}}},{n = 0},\ldots\mspace{14mu},131,{u = 0},\ldots\mspace{14mu},125}{{{{bq}(n)} = {{Hadamard}_{5q}^{128 \times 128}( {{mod}( {n,128} )} )}},{n = 0},\ldots\mspace{14mu},131,{q = 0},1,2,3}{{{C_{k}(n\;)} = e^{{- j}\frac{2\;\pi\; 32{kn}}{132}}},{n = 0},\ldots\mspace{14mu},131,{k = 0},1,2,3}{{u = {{mod}( {{PCID},126} )}},{q = \lfloor \frac{PCID}{126} \rfloor},{k = {{Subframe}\mspace{14mu}{indication}}}}} & \lbrack {{Equation}\mspace{14mu} 18} \rbrack\end{matrix}$

Equation 19 below shows an NB-SSS (d(n)) according to another embodimentof the present invention, which corresponds to an example of configuringthe Hadamard sequence and a sequence for the cyclic shift.

$\begin{matrix}{{d(n)} = {{b_{q}(m)}e^{{- j}\; 2\;\pi\;\theta_{f}n}{e^{{- j}\frac{\pi\;{{un}^{\prime}{({n^{\prime} + 1})}}}{131}}.}}} & \lbrack {{Equation}\mspace{14mu} 19} \rbrack\end{matrix}$

In Equation 19, the following equations are satisfied.

n = 0, 1, …  , 131 n^(′) = n mod 131 m = n mod 128u = N_(ID)^(Ncell)mod 126 + 3$q = \lfloor \frac{N_{ID}^{Ncell}}{126} \rfloor$

Meanwhile, in Equation 19, a binary sequence b_(q)(m) can be given asshown in Table 16.

TABLE 16 q b_(q) (0), . . . , b_(q) (127) 0 [1 1 1 1 1 1 1 1 1 1 1 1 1 11 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 11 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 11 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 11 1 1 1 1 1] 1 [1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 1 −1 −1 1 −1 1 1 −1 1 −1−1 1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 1 −1 −1 1 −1 1 1−1 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 1 −1 −1 1−1 1 1 −1 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 1−1 −1 1 −1 1 1 −1 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1] 2 [1 −1 −1 1 −1 1 1 −1−1 1 1 −1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 1−1 −1 1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 1 −1 −1 1 1 −1−1 1 −1 1 1 −1 −1 1 1 −1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 1 −1 −1 1−1 1 1−1 −1 1 1 −1 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 −1 1 1 −1 −1 1 1 −11 −1 −1 1] 3 [1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 1 −1 −1 1 −1 1 1 −1 1 −1 −11 1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1−1 1 1 −1 −1 1 1 −1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1 1−1 −1 1 −1 1 1 −1 −1 1 1 −1 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 1 −1−1 1 −1 1 1 −1 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1]

In addition, in Equation 19, a cyclic shift value θ_(f) in a framenumber of can be defined according to Equation 20.

$\begin{matrix}{\theta_{f} = {\frac{33}{132}( {n_{f}\text{/}2} ){mod}\; 4}} & \lbrack {{Equation}\mspace{14mu} 20} \rbrack\end{matrix}$

Resource Structure

Hereinafter, the overall resource structure of the system where theabove-described NB-PSS and NB-SSS are applied will be described.

FIG. 15 illustrates an exemplary downlink/uplink (DL/UL) slot structureof the wireless communication system.

Referring to FIG. 15, a slot includes a plurality of orthogonalfrequency division multiplexing (OFDM) symbols in the time domain and aplurality of resource blocks (RBs) in the frequency domain. The OFDMsymbol means one symbol interval. Referring to FIG. 15, a signaltransmitted in each slot may be represented by a resource grid composedof N^(DL/UL) _(RB)×N^(RB) _(sc) subcarriers and N^(DL/UL) _(symb) OFDMsymbols. Here, N^(DL) _(RB) indicates the number of resource blocks(RBs) in a DL slot, and N^(UL) _(RB) indicates the number of RBs in a ULslot. N^(DL) _(RB) and N^(DL) _(RB) depend on DL transmission bandwidthand UL transmission bandwidth, respectively. N^(DL) _(symb) denotes thenumber of OFDM symbols in a DL slot, and N^(UL) _(symb) denotes thenumber of OFDM symbols in a UL slot. N^(RB) _(sc) denotes the number ofsubcarriers constructing one RB.

The OFDM symbol may be referred to as a single carrier frequencydivision multiplexing (SC-FDM) symbol or the like according to multipleaccess schemes. The number of OFDM symbols included in one slot can bevariously changed according to cyclic prefix (CP) lengths. For example,one slot includes seven OFDM symbols in the case of a normal CP, and itincludes six OFDM symbols in the case of an extended CP. For convenienceof description, although FIG. 12 shows that 7 OFDM symbols are includedin one slot of the subframe, the embodiments of the present inventioncan be equally applied to subframes having different numbers of OFDMsymbols.

Referring to FIG. 15, each OFDM symbol includes N^(DL/UL) _(RB)×N^(RB)_(sc) subcarriers in the frequency domain. The subcarrier may be dividedinto the following types: a data subcarrier for data transmission; areference signal subcarrier for transmission of a reference signal; anda null subcarrier for a guard band or a direct current (DC) element. TheDC element is mapped to a carrier frequency f0 during an OFDM signalgeneration process or a frequency up-conversion process. The carrierfrequency is also referred to as a center frequency fc.

One RB is defined as N^(DL/UL) _(symb) (e.g., 7) consecutive OFDMsymbols in the time domain and N^(RB) _(sc) (e.g., 1) consecutivesubcarriers in the frequency domain. For reference, the resourcecomposed of one OFDM symbol and one subcarrier is referred to as aresource element (RE) or tone. Accordingly, one RB is composed ofN^(DL/UL) _(symb)×N^(RB) _(sc), REs. Each RE in the resource grid may beuniquely defined by an index pair (k, 1) in one slot. Here, k indicatesan index from 0 to N^(DL/UL) _(RB)×N^(RB) _(sc)−1 in the frequencydomain, and l indicates an index from 0 to N^(DL/UL) _(symb)−1 in thetime domain.

Meanwhile, one RB is mapped to one physical resource block (PRB) and onevirtual resource block (VRB). In the time domain, the PRB is defined byN^(DL/UL) _(symb) (e.g., 7) consecutive OFDM symbols or SC-FDM symbols.In the frequency domain, the PRB is defined by N^(RB) _(sc) (e.g., 12)consecutive subcarriers. Accordingly, one PRB is composed of N^(DL/UL)_(symb)×N^(RB) _(sc) REs. Two RBs respectively located in two slots ofthe subframe while occupying the same N^(RB) _(sc) consecutivesubcarriers in one subframe are referred to as a PRB pair. Two RBsconstituting the PRB pair have the same PRB number (or PRB index).

FIG. 16 illustrates an exemplary DL subframe structure used in thewireless communication system.

Referring to FIG. 16, a DL subframe is divided into a control region anda data region in the time domain. As shown in FIG. 16, up to first three(four) OFDM symbols of the first slot in the subframe corresponds to thecontrol region to which a control channel is allocated. Hereinafter, aresource region available for PDCCH transmission in a DL subframe isreferred to as a PDCCH region. The remaining OFDM symbols other than theOFDM symbol(s) used for the control region correspond to the data regionto which a physical downlink shared channel (PDSCH) is allocated.Hereinafter, a resource region available for PDSCH transmission in a DLsubframe is referred to as a PDSCH region. Examples of the downlinkcontrol channels include, for example, a physical control formatindicator channel (PCFICH), a physical downlink control channel (PDCCH),a physical hybrid automatic repeat request indicator channel (PHICH),etc. The PCFICH is transmitted at the first OFDM symbol of a subframeand carries information on the number of OFDM symbols used fortransmitting a control channel in the subframe. The PHICH carries ahybrid automatic repeat request (HARQ)acknowledgement/negative-acknowledgement (ACK/NACK) signal in responseto uplink transmission.

The control information transmitted through the PDCCH is referred to asdownlink control information (DCI). The DCI includes resource allocationinformation and other control information for a UE or UE group. Thetransmit format and resource allocation information of a downlink sharedchannel (DL-SCH) is also referred to as DL scheduling information or aDL grant, and the transmit format and resource allocation information ofan uplink shared channel (UL-SCH) is referred to as UL schedulinginformation or a UL grant. The size and usage of the DCI carried by onePDCCH may vary according to DCI formats, and the size may also varyaccording to coding rates. In the current 3GPP LTE system, formats 0 and4 have been defined for uplink and various formats 1, 1A, 1B, 1C, 1D, 2,2A, 2B, 2C, 3, 3A, etc. have been defined for downlink. According tousage of each DCI format, any combination of control information such ashopping flag, RB allocation, modulation and coding scheme (MCS),redundancy version (RV), new data indicator (NDI), transmit powercontrol (TPC), cyclic shift demodulation reference signal (DM RS), ULindex, channel quality information (CQI) request, DL assignment index,HARQ process number, transmitted precoding matrix indicator (TPMI),precoding matrix indicator (PMI), etc. is transmitted to a UE asdownlink control information.

A plurality of PDCCHs can be transmitted in the control region. A UE canmonitor the plurality of PDCCHs, and an eNB determines a DCI formataccording to DCI to be transmitted to a UE and attaches cyclicredundancy check (CRC) to the DCI. The CRC is masked (or scrambled) withan identifier (e.g., radio network temporary identifier (RNTI))according to an owner or usage of the PDCCH. For example, if the PDCCHis for a specific UE, an identifier of the UE (e.g., cell-RNTI (C-RNTI))may be masked to the CRC. If the PDCCH is for a paging message, a pagingidentifier (e.g., paging radio network temporary identifier (P-RNTI))may be masked to the CRC. If the PDCCH is for system information (morespecifically, a system information block (SIB)), a system informationRNTI (SI-RNTI) may be masked to the CRC. If the PDCCH is for randomaccess response, a random access-RNTI (RA-RNTI) may be masked to theCRC. For example, CRC masking (or scrambling) includes XOR operation ofthe CRC and RNTI at a bit level.

The PDCCH is transmitted on aggregation of one or a plurality ofconsecutive control channel elements (CCEs). The CCE is a logicalallocation unit used to provide the PDCCH with a coding rate based onthe state of a radio channel. The CCE corresponds to a plurality ofresource element groups (REGs). For example, one CCE corresponds to nineREGs, and one REG corresponds to four REs. Four QPSK symbols are mappedto each REG. The RE occupied by a reference signal (RS) is not includedin the REG. Accordingly, the number of REGs in a given OFDM symbolvaries depending on whether the RS is present. The concept of the REG isalso applied to other downlink control channels (e.g., PCFICH andPHICH). The DCI format and the number of DCI bits are determinedaccording to the number of CCEs. The CCEs are numbered and consecutivelyused and, in order to simplify a decoding process, the PDCCH having aformat composed of n CCEs can start at only a CCE having a numbercorresponding to a multiple of n. The number of CCEs used fortransmitting a specific PDCCH is determined according to the channelstate or by the network or eNB. For example, if the PDCCH is for a UEhaving a good DL channel (e.g., adjacent to the eNB), only one CCE canbe sufficient. However, if the PDCCH is for a UE having a poor channelstate (e.g., located near a cell edge), eight CCEs may be required toobtain sufficient robustness. In addition, the power level of the PDCCHmay be controlled according to the channel state.

Apparatus Configuration

FIG. 17 is a block diagram showing the components of a transmittingdevice 10 and a receiving device 20 for performing embodiments of thepresent invention.

The transmitting device 10 and the receiving device 20 include radiofrequency (RF) units 13 and 23 for transmitting or receiving a radiosignal carrying information and/or data, a signal and a message,memories 12 and 22 for storing a variety of information associated withcommunication in a wireless communication system, and processors 11 and21 operatively connected to the components including the RF units 13 and23 and the memories 12 and 22 and configured to control the memories 12and 22 and/or the RF units 13 and 23 to perform at least one of theembodiments of the present invention, respectively.

The memories 12 and 22 may store programs for processing and controllingthe processors 11 and 21 and may temporarily store input/output signal.The memories 12 and 22 may be used as a buffer.

The processors 11 and 21 generally control the overall operation of thevarious modules of the transmitting device and the receiving device. Inparticular, the processors 11 and 21 may perform a variety of controlfunctions for performing the present invention. The processors 11 and 21may be referred to as a controller, a microcontroller, a microprocessor,a microcomputer, etc. The processors 11 and 21 can be implemented by avariety of means, for example, hardware, firmware, software, or acombination thereof. In the case of implementing embodiments of thepresent invention by hardware, application specific integrated circuits(ASICs), Digital signal processors (DSPs), digital signal processingdevices (DSPDs), programmable logic devices (PLDs), field programmablegate arrays (FPGAs), etc. configured to perform embodiments of thepresent invention may be included in the processors 11 and 21. Ifoperations or functions of embodiments of the present invention areimplemented by firmware or software, firmware or software may beconfigured to include modules, procedures, functions, etc. forperforming the functions or operations of embodiments of the presentinvention. The firmware or software configured to perform embodiments ofthe present invention may be included in the processors 11 and 21 orstored in the memories 12 and 22 so as to be operated by the processors11 and 21.

The processor 11 of the transmitting device 10 performs coding andmodulation with respect to a signal and/or data which is scheduled bythe processor 11 or a scheduler connected to the processor 11 to betransmitted to an external device and transmits the signal and/or datato the RF unit 13. For example, the processor 11 transforms a datastream to be transmitted into K layers via demultiplexing and channelcoding, scrambling, modulation, etc. The coded data stream is alsocalled a codeword and is equivalent to a transport block which is a datablock provided by a medium access control (MAC) layer. One transportblock (TB) is encoded into one codeword and each codeword is transmittedto the receiver in the form of one or more layers. For frequencyup-conversion, the RF unit 13 may include an oscillator. The RF unit 13may include N_(t) (N_(t) being a positive integer) transmit antennas.

Signal processing of the receiving device 20 is the inverse of signalprocessing of the transmitting device 10. Under control the processor21, the RF unit 23 of the receiving device 20 receives a radio signaltransmitted by the transmitting device 10. The RF unit 23 may includeN_(r) (N_(r) being a positive integer) receive antennas and the RF unit23 performs frequency down-conversion with respect to each signalreceived via each receive antenna and restores a baseband signal. The RFunit 23 may include an oscillator for frequency down-conversion. Theprocessor 21 may perform decoding and demodulation with respect to theradio signal received via the receive antennas and restore original datatransmitted by the transmitting device 10.

Each of the RF units 13 and 23 includes one or more antennas. Theantennas serve to transmit the signals processed by the RF units 13 and23 to external devices or to receive radio signals from external devicesand to send the radio signals to the RF units 13 and 23 under control ofthe processors 11 and 21 according to one embodiment of the presentinvention. The antennas are also called antenna ports. Each antenna maybe composed of one physical antenna or a combination of more than onephysical antenna elements. The signal transmitted by each antenna is notdecomposed by the receiving device 20. A reference signal (RS)transmitted in correspondence with the antenna defines the antennaviewed from the viewpoint of the receiving device 20 and enables thereceiving device 20 to perform channel estimation of the antennaregardless of whether the channel is a single radio channel from asingle physical antenna or a composite channel from a plurality ofphysical antennal elements including the above antennas. That is, theantenna is defined such that the channel for delivering a symbol overthe antenna is derived from the channel for delivering another symbolover the same antenna. In case of the RF unit supporting a multipleinput multiple output (MIMO) function for transmitting and receivingdata using a plurality of antennas, two or more antennas may beconnected.

In the embodiments of the present invention, a UE operates as thetransmitting device 10 in uplink and operates as the receiving device 20in downlink. In the embodiments of the present invention, an eNBoperates as the receiving device 20 in uplink and operates as thetransmitting device 10 in downlink. Hereinafter, the processor, the RFunit and the memory included in the UE are respectively referred to as aUE processor, a UE RF unit and a UE memory and the processor, the RFunit and the memory included in the eNB are respectively referred to asan eNB processor, an eNB RF unit and an eNB memory.

The detailed description of the exemplary embodiments of the presentinvention has been given to enable those skilled in the art to implementand practice the invention. Although the invention has been describedwith reference to the exemplary embodiments, those skilled in the artwill appreciate that various modifications and variations can be made inthe present invention without departing from the spirit or scope of theinvention described in the appended claims. Accordingly, the inventionshould not be limited to the specific embodiments described herein, butshould be accorded the broadest scope consistent with the principles andnovel features disclosed herein.

INDUSTRIAL APPLICABILITY

The present invention is applicable to various wireless systemssupporting narrowband communication in order to provide an IoT servicein addition to a wireless communication system for providing an IoTservice based on an LTE system.

What is claimed is:
 1. A method for transmitting a narrowband (NB)synchronization signal to at least one user equipment (UE) by an evolvednode B (eNB) in a wireless communication system, the method comprising:repeating a first Zadoff-Chu sequence on a plurality of orthogonalfrequency division multiplexing (OFDM) symbols, the first Zadoff-Chusequence having only one predefined root index; transmitting therepeated Zadoff-Chu sequence as an NB primary synchronization signal (NBPSS) of the NB synchronization signal; wherein the NB PSS is transmittedin a state in which the first Zadoff-Chu sequence is multiplied in eachof the plurality of OFDM symbols by each element of a cover sequencehaving a length corresponding to the number of the plurality of OFDMsymbols; and transmitting a second Zadoff-Chu sequence as an NBsecondary synchronization signal (NB SSS) of the NB synchronizationsignal for identifying an NB cell identifier, wherein the NB SSS istransmitted in a state in which the second Zadoff-Chu sequence ismultiplied by each element of a scrambling sequence having a lengthcorresponding to a length of the second Zadoff-Chu sequence, and whereina multiplication between the first Zadoff-Chu sequence and the coversequence is in a unit of OFDM symbol while a multiplication between thesecond Zadoff-Chu sequence and the scrambling sequence is in a unit ofan element of each sequence.
 2. The method of claim 1, wherein the NBsynchronization signal is a synchronization signal transmitted forperforming Internet of Things (IoT) communication operation through anarrow band corresponding to partial system bandwidth of the wirelesscommunication system.
 3. The method of claim 1, wherein the plurality ofOFDM symbols are consecutively arranged in a time domain.
 4. The methodof claim 1, wherein the number of the plurality of OFDM symbols is equalto a difference between the number of OFDM symbols included in onesubframe and the number of OFDM symbols available for transmission of aphysical downlink control channel (PDCCH).
 5. The method of claim 1,wherein subcarrier spacing in a resource region where the NBsynchronization signal is transmitted is 15 kHz.
 6. A method forreceiving a narrowband (NB) synchronization signal from an evolved nodeB (eNB) by a user equipment (UE) in a wireless communication system, themethod comprising: receiving an NB primary synchronization signal (NBPSS) of the NB synchronization signal generated by repetition of a firstZadoff-Chu sequence on a plurality of orthogonal frequency divisionmultiplexing (OFDM) symbols, the first Zadoff-Chu sequence having onlyone predefined root index; and receiving an NB secondary synchronizationsignal (NB SSS) of the NB synchronization signal based on a secondZadoff-Chu sequence for identifying an NB cell identifier, wherein theNB PSS is received in a state in which the first Zadoff-Chu sequence ismultiplied in each of the plurality of OFDM symbols by each element of acover sequence having a length corresponding to the number of theplurality of OFDM symbols, wherein the NB SSS is received in a state inwhich the second Zadoff-Chu sequence is multiplied by each element of ascrambling sequence having a length corresponding to a length of thesecond Zadoff-Chu sequence, and wherein a multiplication between thefirst Zadoff-Chu sequence and the cover sequence is in a unit of OFDMsymbol while a multiplication between the second Zadoff-Chu sequence andthe scrambling sequence is in a unit of an element of each sequence. 7.The method of claim 6, wherein the NB synchronization signal is asynchronization signal for performing Internet of Things (IoT)communication operation through a narrow band corresponding to partialsystem bandwidth of the wireless communication system.
 8. The method ofclaim 6, wherein the plurality of OFDM symbols are consecutivelyarranged in a time domain.
 9. The method of claim 6, wherein the numberof the plurality of OFDM symbols is equal to a difference between thenumber of OFDM symbols included in one subframe and the number of OFDMsymbols available for transmission of a physical downlink controlchannel (PDCCH).
 10. The method of claim 6, wherein subcarrier spacingin a resource region where the NB synchronization signal is received is15 kHz.
 11. An evolved node B (eNB) for transmitting a narrowband (NB)synchronization signal to at least one user equipment (UE) in a wirelesscommunication system, the eNB comprising: a processor configured to:generate an NB primary synchronization signal (NB PSS) of the NBsynchronization signal by repeating a first Zadoff-Chu sequence on aplurality of orthogonal frequency division multiplexing (OFDM) symbols,the first Zadoff-Chu sequence having only one predefined root index, andgenerate an NB secondary synchronization signal (NB SSS) of the NBsynchronization signal based on a second Zadoff-Chu sequence foridentifying an NB cell identifier; and a transceiver connected to theprocessor and configured to transmit the NB PSS and the NB SSS to the atleast one UE, wherein the processor is configured to generate the NB PSSby multiplying, in a unit of OFDM symbol, the first Zadoff-Chu sequenceand each element of a predetermined cover sequence having a lengthcorresponding to the number of the plurality of OFDM symbols, andwherein the processor is configured to generate the NB SSS bymultiplying, in a unit of an element of each sequence, the secondZadoff-Chu sequence and a scrambling sequence having a lengthcorresponding to a length of the second Zadoff-Chu sequence.
 12. The eNBof claim 11, wherein the number of the plurality of OFDM symbols isequal to a difference between the number of OFDM symbols included in onesubframe and the number of OFDM symbols available for transmission of aphysical downlink control channel (PDCCH).
 13. A user equipment (UE) forreceiving a narrowband (NB) synchronization signal from an evolved nodeB (eNB) in a wireless communication system, the UE comprising: atransceiver configured to: receive an NB primary synchronization signal(NB PSS) of the NB synchronization signal generated by repetition of afirst Zadoff-Chu sequence on a plurality of orthogonal frequencydivision multiplexing (OFDM) symbols, the first Zadoff-Chu sequencehaving only one predefined root index, and receive an NB secondarysynchronization signal (NB SSS) of the NB synchronization signal basedon a second Zadoff-Chu sequence for identifying an NB cell identifier;and a processor configured to process the NB PSS and the NB SSS receivedby the transceiver, wherein the NB PSS is received in a state in whichthe first Zadoff-Chu sequence is multiplied in each of the plurality ofOFDM symbols by each element of a cover sequence having a lengthcorresponding to the number of the plurality of OFDM symbols, whereinthe NB SSS is received in a state in which the second Zadoff-Chusequence is multiplied by each element of a scrambling sequence having alength corresponding to a length of the second Zadoff-Chu sequence, andwherein a multiplication between the first Zadoff-Chu sequence and thecover sequence is in a unit of OFDM symbol while a multiplicationbetween the second Zadoff-Chu sequence and the scrambling sequence is ina unit of an element of each sequence.
 14. The UE of claim 13, whereinthe number of the plurality of OFDM symbols is equal to a differencebetween the number of OFDM symbols included in one subframe and thenumber of OFDM symbols available for transmission of a physical downlinkcontrol channel (PDCCH).